As radio apparatuses, such as cellular phones, have spread, multiple peripheral devices, such as earphones and microphones, to be connected to the radio apparatuses have been developed.
Generally, the peripheral devices and the radio apparatuses are connected by connection cables.
A communication function is a basic function for a radio apparatus, and the performance of this function is important.
Therefore, for example, in patent document 1 is proposed an earphone wire whereby, as shown in FIG. 11, a signal line 31 in a connection cable is used as an antenna to complement the communication performance of a radio apparatus. Furthermore, in patent document 2 is disclosed an earphone cable whereby, as shown in FIG. 12, an antenna device 32 is arranged at the portion of a connection cable near the main body of a radio apparatus (see patent documents 1 and 2).
Patent Document 1: JP-A-2002-314450
Patent Document 2: JP-A-2000-349868